Use of Solid-phase Microextraction (SPME) to Investigate ... · Elliott Bay surface water results...

Region 10Seattle DistrictEnvironmental And Water ResourcesU of Texas, Austin

Objectives

Illustrate preparation & use of Solid-Phase Microextraction (SPME) technique

Answer specific questions regarding the remedial cap: Do PAHs in sediment porewater currently exceed Ambient Water

Quality Standards (AWQS)? Are there upwelling trends suggesting groundwater advection and

future cap failure? What is the nature of cap recontamination, if any? What does porewater imply for benthic toxicity?


Why Measure Porewater? To compare near-surface porewater to AWQS, required

by Second PSR Five-Year Review that suggested based on increase in NAPL in wells along shoreline could indicate NAPL migration into adjacent Puget Sound

To determine gradients in cap or in nearshore groundwater zones

(Procedurally) to ascertain “non-steady state” adjustments for slow-to-uptake PAHs due to diffusion limitation in SPME device

To gain an understanding of bioavailability of PAHs


Sampling Strategy for PSR (1) Prior Studies:

EPA Diver Survey to ascertain sediment penetration

Univ. of Texas (UT) Calibration Study to develop fiber association constants

Prepare SMPEs in pushpoint devices Use both 1000/1071 μm and 210/230 μm

polydimethylsiloxane (PDMS) coated fibers (for nonequilibrium corrections)

Confirm fibers are free of PAH Insert into push-point sampler

Deploy and retrieve SMPEs using divers

Clip fiber lengths, extract into acetonitrile

Analyze with HPLC-FD

Inner diameter

=1,000 μm glass

fiber

Outer diameter =35.5 μm PDMS

Id = 210 μm

Outer diameter =10 μm PDMS


Solid Phase Microextraction (SPME) Sampler


Sampling Strategy for PSR (2) SPME Deployment

7 day equilibration period before recovery Subsamples collected immediately – Intervals:

SPME lengths (feet)

# Deployed in Sediment

# Deployed in Surface Water

# of Blanks (shipping and retrieval)

3 15 0 2

2 1 0 0

1 8 3 0

Target Depth (cm) Sample intervals (cm)

0 – 10 3 – 5 and 5 – 7

10 – 20 13 – 15 and 15 – 17

20 – 24 53 – 55 and 55 – 57

27 - 30 70 – 72 and 72 – 74


Interpretation Logic


Surface Water Sampling Locations


Surface Water LPAH

ng/L


Surface Water HPAH (1)

ng/L


ng/L

Surface Water HPAH (2)


Surface Water Conclusions Elliott Bay has higher HPAHs in surface water than a

nearby ambient Puget Sound station

No AWQS were exceeded Elliott Bay surface water results are suitable comparators

to the SPME results


Cap SPME Locations


Pore

wat

er/A

WQ

S

Cap SPME Results Compared to AWQS


Maximum Chrysene Stations: AWQC 18 ng/L


Maximum Phenanthrene & Pyrene Stations

Station 2 Phenanthrene Pyrene

depth (cm) ng/L ng/L

4 134 246 44 4

14 11 4

16 7 2

Station 19 Phenanthrene Pyrene

depth (cm) ng/L ng/L

4 14 316 11 16

14 12 15

16 12 11


SW1SW2

4 cm6 cm

14 cm16 cm

0

20

40

60

80

100

120

140

LPAH in Station 2 Compared to Surface Water (ng/L)

SW1SW2

4 cm6 cm

14 cm16 cm

0

20

40

60

80

100

120

140

LPAH in Station 19 Compared to Surface Water (ng/L)


SW1

SW2

4 cm

6 cm

14 cm16 cm

0

5

10

15

20

25

30

35

40

45

ng/L

HPAH(1) in Station 2 Compared to Surface Water

SW1

SW2

4 cm

6 cm

14 cm16 cm

0

10

20

30

40

50

60

Fluoranthene PyreneChrysene

ng/L

HPAH(1) in Station 19 Compared to Surface Water


SW1SW2

4 cm6 cm

14 cm16 cm

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

B[a]A B[b]F B[k]F B[a]P

ng/L

Four More HPAH in Station 2 Compared to Surface Water

SW1

SW2

4 cm6 cm

14 cm16 cm

0

0.5

1

1.5

2

2.5

3

3.5

B[a]A B[b]FB[k]F

B[a]P

ng/L

Four More HPAH in Station 19Compared to Surface Water


Conclusions for PSR Cap All compounds below AWQS

SPMEs capable of very low levels of resolution

Chrysene Maximum concentration at 59% of the AWQS; apparently related to incoming

sediment (not deep upwelling)

Most other compounds in porewater : 1-4 orders of magnitude below AWQS

Surface water was below AWQS Near-surface cap (4 - 6 cm) were higher than surface water but below AWQS

No upward trend Thus, no evidence of a bottom-up contamination

Possible top-down contamination pattern from incoming sediment Trend is not critical at this time given the magnitude of dissolved PAH


Why Use Passive Samplers? Measuring Bioavailability without SPME Prediction of toxicity – from EPA (2003) and EPA (2007):

Use Equilibrium Partitioning (EqP) to determine concentration

Calculate the ratios of individual PAHs to their Final Chronic Values (“Toxicity Units”, TU)

Add these to determine ΣTU

Compare to a ΣTU of 1.0 – the probable effect level using the narcosis model

Caveats: EqP overestimates toxicity by c 100x.

Also, “black carbon” adjusted EqP tends to underpredict toxicity (Gschwend, et al. 2010)


Why Use Passive Samplers? Measuring Bioavailability with SPME SPME measures porewater directly

SPMEs are better benthic toxicity estimators than bulk sediment PAH

Usually, results are within a factor of 2, as opposed to 100 for EqP alone

Total Toxicity of all surface stations are far below 1.0 Stations with highest sediment surface concentrations

evaluated on next slide

Other passive samplers are quite comparable to SPME (the main differences are the logistics of deployment –SPME are better for penetrating a cap)


Toxicity Units Calculation, Stations 2 and 19

Sampler 2, 4 cm ng/L FCV TUUncertainty Adjusted TU Sampler 19, 4 cm ng/L FCV TU

Uncertainty Adjusted TU

Naphthalene 14.792 193500 7.64E-05 7.64E-05 Naphthalene 116.03 193500 6.00E-04 6.00E-04

2-MNP 69.644 72160 9.65E-04 9.65E-04 2-MNP 12.197 72160 1.69E-04 1.69E-04

Fluorene 10.597 39300 2.70E-04 2.70E-04 Fluorene 0 39300 0.00E+00 0.00E+00

Acenaphthene 31.036 306900 1.01E-04 1.01E-04 Acenaphthene 11.865 306900 3.87E-05 3.87E-05

Phenanthrene 134.153 19130 7.01E-03 7.01E-03 Phenanthrene 14.372 19130 7.51E-04 7.51E-04

Anthracene 18.42 20730 8.89E-04 8.89E-04 Anthracene 12.331 20730 5.95E-04 5.95E-04

Fluoranthene 41.794 7109 5.88E-03 5.88E-03 Fluoranthene 57.033 7109 8.02E-03 8.02E-03

Pyrene 23.519 10110 2.33E-03 2.33E-03 Pyrene 31.408 10110 3.11E-03 3.11E-03

Chrysene 4.263 2042 2.09E-03 2.09E-03 Chrysene 10.592 2042 5.19E-03 5.19E-03

B[a]A 1.964 22270 8.82E-05 8.82E-05 B[a]A 3.119 22270 1.40E-04 1.40E-04

B[b]F 4.141 677.4 6.11E-03 1.22E-02 B[b]F 2.355 677.4 3.48E-03 6.95E-03

B[k]F 1.566 641.5 2.44E-03 4.88E-03 B[k]F 0.744 641.5 1.16E-03 2.32E-03

B[a]P 2.02 957.3 2.11E-03 4.22E-03 B[a]P 0.76 957.3 7.94E-04 1.59E-03

TU Sum 0.030 0.041 TU Sum 0.024 0.029


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Use of Solid-phase Microextraction (SPME) to Investigate ... · Elliott Bay surface water results...

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